Oil Burning Underwater: What Actually Happens In Water
- 01. The Science Behind Combustion and Water
- 02. In Situ Burning: When Oil Burns on Water Surfaces
- 03. Key Requirements for Oil to Burn on Water
- 04. Historical Timeline of In Situ Burning Research
- 05. Combustion Dynamics: Experimental Data and Burning Rates
- 06. Arctic Oil Spills and Ice Interaction
- 07. Environmental Trade-offs of In Situ Burning
- 08. Modern Applications and Future Research Directions
No, oil cannot burn when it is fully submerged underwater because combustion requires oxygen from the air, and water displaces the oxygen needed for the fire reaction. However, oil can and does burn on the surface of water, which is why controlled burns are used worldwide to clean up oil spills. The flames appear to float because oil is less dense than water and forms a separate layer on top where it can access atmospheric oxygen.
The Science Behind Combustion and Water
Combustion is a chemical reaction that requires three elements: fuel, heat, and oxygen. This is known as the fire triangle. When oil is completely submerged underwater, water surrounds the fuel molecules and prevents them from contacting oxygen gas (O₂) in sufficient concentration to sustain a flame. Water molecules (H₂O) are already fully oxidized hydrogen, meaning they cannot support further combustion reactions.
The density difference between oil and water is critical to understanding why oil fires appear to burn on water. Most crude oils have a density of approximately 0.80-0.95 g/cm³, while water has a density of 1.00 g/cm³. This means oil floats, creating a thin layer where combustion can occur at the oil-air interface, not within the water itself.
In Situ Burning: When Oil Burns on Water Surfaces
During the historic Deepwater Horizon oil spill in April 2010, crews began igniting parts of the spill in discrete patches on the Gulf of Mexico surface. This technique, called in situ burning, was used to remove an estimated 220,000-310,000 barrels of oil from the ocean surface. The operation demonstrated that burning is the most efficient, rapid, and environmentally friendly option for cleaning up certain open water oil spills.
Penn State researchers published breakthrough findings showing that diesel fuel emulsions up to 80 percent water and crude oil emulsions up to 35 percent water can still be ignited under laboratory conditions. This expanded the applicability of burning beyond what scientists previously believed possible, as emulsions were historically thought to be incombustible.
Key Requirements for Oil to Burn on Water
Not all oil spills can be ignited confidently. Several specific conditions must be met for successful in situ burning:
- The oil must be contained using fireproof floating barriers to prevent uncontrolled spread
- The oil layer must be at least 2-3 mm thick to sustain combustion
- The oil cannot have too much water mixed in (typically less than 30-40% water content)
- Volatile elements that ignite easiest must not have evaporated yet
- Stormy seas can stymie ignition efforts due to wave action dispersing the oil
- An external radiant heat source is often needed to facilitate initial ignition
Historical Timeline of In Situ Burning Research
- 1958 - First documented use of in situ burning for oil spill cleanup
- 1970s-1980s - Early research establishes minimum oil thickness requirements for ignition
- 1989 - Exxon Valdez spill uses controlled burns, removing approximately 4-6% of spilled oil
- 2010 - Deepwater Horizon spill sees largest systematic in situ burning operation in history, with 413 controlled burns conducted
- 2014 - Study reveals oil burns faster in ice than in other materials, complicating Arctic spill response
- 2023 - New research examines burning dynamics with immersed conductive objects on turbulent water surfaces
Combustion Dynamics: Experimental Data and Burning Rates
Recent experimental research has quantified how underwater objects and water turbulence affect oil burning rates. A 2023 study published in Combustion and Flame examined dodecane and heptane burning on turbulent water surfaces with immersed copper rods.
| Fuel Type | Condition | Burning Rate Change | Primary Mechanism |
|---|---|---|---|
| Dodecane | Quiescent water, copper rod present | Decreased 28% | Nucleate boiling behavior |
| Heptane | Quiescent water, copper rod present | Increased 13% | Nucleate boiling behavior |
| Dodecane | Turbulent water, copper rod present | Decreased (significant) | Heat loss from immersed rod |
| Heptane | Turbulent water, copper rod present | Decreased (significant) | Heat loss from immersed rod |
| Diesel emulsion | Up to 80% water content | Still ignitable | External heat source required |
| Crude oil emulsion | Up to 35% water content | Still ignitable | External heat source required |
The turbulence intensity in these experiments ranged from 0.017 to 0.033 m/s, which significantly impacted nucleate boiling behaviors observed on immersed sections. This data is critical for predicting how oil spills will behave in real ocean conditions with waves and currents.
Arctic Oil Spills and Ice Interaction
A 2014 study revealed surprising findings about how petroleum burns in frozen conditions. The team found that oil actually burned much faster in ice than in other containment materials. The heat from combustion widened the ice bowls and thinned the oil layer, allowing faster burning than expected.
However, this created a troubling discovery: during burns, some oil expanded sideways and seeped into the ice, creating bubbles of spilled oil trapped within icebergs. This sooty residue remains unrecoverable until the ice melts, which could take months or years later. Fire protection engineer Ali Rangwala from WPI warned that in situ burning in Arctic spills might actually make environmental contamination worse.
Environmental Trade-offs of In Situ Burning
While burning oil at sea causes significant smoke production, scientists and wildlife experts concluded it may have fewer environmental effects than allowing oil to reach shorelines. The literature suggests burning crude may result in oil that is less sticky and therefore easier for cleanup personnel to deal with.
However, burning can be a difficult maneuver requiring precise conditions. First, portions of the slick must be corralled into confined areas using fireproof floating barriers. The oil cannot have too much water mixed in, and volatile elements must not have evaporated yet. Stormy seas can completely stymie ignition efforts due to wave action dispersing the oil layer too thin.
Modern Applications and Future Research Directions
If a leak occurs in an underwater pipeline, large amounts of liquid petroleum products may spread to the sea surface where ignition may lead to fire, making understanding these dynamics critical for offshore safety. The mathematical models developed in recent studies now include effects of immersed rods and turbulent water sublayers, enabling more accurate predictions for practical oil spill clean-up by burning.
A parametric study using these validated models shows the influence of multiple immersed rods and their corresponding implications for practical applications. This research directly informs environmental response strategies, helping emergency teams determine when controlled burns are feasible versus when alternative cleanup methods like absorption pads and booms are more effective.
The fundamental principle remains clear: oil requires oxygen to burn, water prevents oxygen access when fully submerging fuel, but oil floating on water surface can and does burn efficiently when properly contained and ignited. This scientific understanding enables emergency responders to make evidence-based decisions about spill mitigation strategies worldwide.
Key concerns and solutions for Oil Burning Underwater What Actually Happens In Water
Can oil burn if it is completely underwater?
No, oil cannot burn when completely submerged underwater because water prevents contact between fuel molecules and atmospheric oxygen, which is essential for combustion. The fire triangle requires oxygen, fuel, and heat-water removes the oxygen component entirely when fully submerging the fuel.
Why does oil fire appear to float on water?
Oil floats on water because it is less dense (0.80-0.95 g/cm³) than water (1.00 g/cm³), creating a separate layer on the surface where combustion occurs at the oil-air interface, making flames appear to float on the water surface.
What is in situ burning and when is it used?
In situ burning is a controlled spill response technique where oil is intentionally ignited on the water surface to remove it quickly. It requires oil thickness of at least 2-3 mm, water content below 30-40%, and calm sea conditions. First used in 1958, it removed 220,000-310,000 barrels during Deepwater Horizon.
Can oil-water emulsions still burn?
Yes, Penn State researchers demonstrated that diesel fuel emulsions up to 80 percent water and crude oil emulsions up to 35 percent water can still be ignited when an external radiant heat source is positioned near the spill. This expanded what was previously considered combusted oil.
Why don't we put water on oil fires?
Pouring water on an oil fire causes the water to boil instantly, creating steam bubbles that pop and spew burning oil droplets into the air where they access more oxygen, making the fire flare up and spread. The boiling water essentially disperses the fuel rather than extinguishing it.
How much oil was burned during Deepwater Horizon?
During the 2010 Deepwater Horizon disaster, crews conducted 413 controlled burns that removed an estimated 220,000-310,000 barrels of oil from the Gulf of Mexico surface, representing one of the largest systematic in situ burning operations in history.